1. Field
Embodiments of the present invention relate to an integrated electronic hydraulic brake system including an actuator having a master cylinder and a pedal simulator, an electronic stability control (ESC), and a hydraulic power unit (HPU) which are configured as a single unit.
2. Description of the Related Art
Recently, development of hybrid vehicles, fuel cell vehicles and electric vehicles has been vigorously carried out in order to improve fuel efficiency and reduce exhaust gas. A brake device, i.e., a brake device of a brake system for vehicles, which functions to decelerate or stop a vehicle, is essentially installed in such vehicles.
In general, brake devices of brake systems for vehicles include a vacuum brake to generate braking force using suction pressure of an engine, and a hydraulic brake to generate braking force using hydraulic pressure.
The vacuum brake produces large braking force with a small force through a vacuum booster using a difference between suction pressure of a vehicle engine and atmospheric pressure. That is, the vacuum brake generates output greater than force applied to a brake pedal when a driver pushes the brake pedal.
In case of such a conventional vacuum brake, suction pressure of the vehicle engine is supplied to the vacuum booster to form a vacuum, and therefore, fuel efficiency is lowered. Further, the engine is driven at all times to form the vacuum even when the vehicle is stopped.
Furthermore, a fuel cell vehicle and an electric vehicle have no engine and thus application of the conventional vacuum brake boosting the driver's pedal force during braking to the fuel cell vehicle and the electric vehicle may not be allowed, and a hybrid vehicle implements an idle stoppage function during stopping to improve fuel efficiency and requires introduction of a hydraulic brake.
That is, since implementation of a regenerative braking function is required to improve fuel efficiency in all vehicles, the regenerative braking function is easily implemented by employing a hydraulic brake.
In case of an electronic hydraulic brake system which is a kind of hydraulic brake, when a driver pushes a pedal, an electronic control unit senses pushing of the pedal and supplies hydraulic pressure to a master cylinder, thereby transmitting hydraulic pressure for braking to a wheel cylinder (not shown) of each wheel to generate braking force.
In order to control hydraulic pressure transmitted to wheel cylinders 20, the electronic hydraulic brake system includes, as shown in FIG. 1, an actuator 1 including a master cylinder 1a, booster 1b, reservoir 1c and pedal simulator 1d, an electronic stability control (ESC) 2 to independently control braking force to each wheel, and an hydraulic power unit (HPU) 3 including a motor, pump, accumulator and control valve, which are respectively configured as a unit.
The above units 1, 2 and 3 constituting the electronic hydraulic brake system are separately provided and installed. As a result, it may be necessary to secure a space to install the electronic hydraulic brake system. In addition, the weight of the electronic hydraulic brake system is increased. For these reasons, an advanced electronic hydraulic brake system which secures safety of a vehicle during braking, improves fuel efficiency, and provides proper pedal feel has been required.
Therefore, according to the above requirements, research and development on an electronic hydraulic brake system which has a simple configuration, exhibits normal braking force even when a failure occurs and is easily controlled are underway.